So far, optical systems designed to obtain full 360°-direction (full-panoramic) images by imaging optical systems combined with convex mirrors, rotating elliptic mirrors and rotating parabolic mirrors have been put forward in the following patent publications 1 to 7, etc. What is known as “Chameleon Eye®”, Sony Corp., has also been available.
Among prior optical systems using a reflection optical system to obtain full 360°-direction (full-panoramic) images, there is one made up of a front unit comprising a transparent medium that is rotationally symmetric about a center axis and includes two internal reflecting surfaces and two transmitting surfaces and a rear unit that is rotationally symmetric about the center axis and has positive power, as set forth in patent publications 8 and 9.
Patent Publication 1
JP(A) 11-331654
Patent Publication 2
JP(A) 2002-162567
Patent Publication 3
JP(A) 2002-196438
Patent Publication 4
JP(A) 2003-167195
Patent Publication 5
Japanese Patent No. 2925573
Patent Publication 6
JP(A) 11-183637
Patent Publication 7
JP(A) 2002-233494
Patent Publication 8
U.S. Pat. No. 4,566,763
Patent Publication 9
U.S. Pat. No. 5,473,474
A problem with any of the prior optical systems proposed in patent publications 1 to 7, etc. is that the reflecting optical system becomes bulky.
A problem with “Chameleon Eye” is that when full-panoramic images are picked up with the optical system directing to the zenith, much harmful flare light coming from the zenithal direction causes image quality to go worse. Another problem is that because positive power and negative power are given to the reflecting surfaces in order from the object side, the optical system is unavoidably of the telephoto type where the focal length is generally long with respect to the total length; the reflecting optical system becomes bulky as a result of the inability to reduce the total length.
A problem with either of patent publications 8 and 9 is that when full-panoramic images are picked up with the optical system directing to the zenith, much harmful flare light coming from the zenithal direction causes image quality to become worse, because the effective diameter of the first transmitting surface becomes large as a consequence of the entrance pupil in a section including the center axis being apart from the first transmitting (entrance) surface.
Such being the case, the primary object of the invention is to provide a panoramic attachment optical system and a panoramic optical system for taking an image having a full 360°-direction (full-panoramic) angle of view or projecting an image at a full 360°-direction (full-panoramic) angle of view, which have decreased size, minimized flare light and improved resolving power.